Headband of Intellect. The harpy leader is wearing a headband of intellect, raising her Intelligence score to 19.

Multiattack. The harpy makes two attacks with its claws.

Claws. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 6 (2d4 + 1) slashing damage.

Luring Song. The harpy sings a magical melody. Every humanoid and giant within 300 feet of the harpy that can hear the song must succeed on a DC 14 Wisdom saving throw or be charmed until the song ends. The harpy must take a bonus action on its subsequent turns to continue singing. It can stop singing at any time. The song ends if the harpy is incapacitated.

While charmed by the harpy, a target is incapacitated and ignores the songs of other harpies. If the charmed target is more than 5 feet away from the harpy, the target must move on its turn toward the harpy by the most direct route, trying to get within 5 feet. It doesn't avoid opportunity attacks, but before moving into damaging terrain, such as lava or a pit, and whenever it takes damage from a source other than the harpy, the target can repeat the saving throw. A charmed target can also repeat the saving throw at the end of each of its turns. If the saving throw is successful, the effect ends on it.

A target that successfully saves is immune to this harpy's song for the next 24 hours.

Villain actions

The harpy leader uses the following villain actions, each at the end of the round. 

End of first round:
Deadly Lullaby. The harpy leader uses its Luring Song Action

End of second round:
Kill Them, You Fools!. 4 blood hawk are called to battle, appearing from the skies. Additionally, all other harpies in a 50ft range get to fly 20ft without receiving opportunity attacks.

End of third round:
Maddening screech. The hawk leader screeches with all her might, making all humanoid creatures in a 300ft radius have to succeed on a DC14 Wisdom Saving Throw or fall under the effects of the Confusion spell

Whirling wind. The harpy beats its wings at such a great speed it can stop a projectile coming at her. When the harpy does so, the damage taken from the attack is reduced by 1d10. If the damage is reduced to 0, the projectile deviates and misses the harpy.

Nimble escape. The harpy beats its wings. The harpy gains 30ft flying speed without receiving opportunity attacks.